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8888 



Bureau of Mines Information Circular/1982 



Preliminary Testing of a Prototype 
Portable X-Ray Fluorescence 
Spectrometer 



By Lowell L. Patten, Neal B. Anderson, 
and John J. Stevenson 




UNITED STATES DEPARTMENT OF THE INTERIOR 



[(jjtcjjfrtu - / #*^V^*) > 



Information Circular 8888 

M N 




Preliminary Testing of a Prototype 
Portable X-Ray Fluorescence 
Spectrometer 



By Lowell L. Patten, Neal B. Anderson, 
and John J. Stevenson 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 






afi 



K\0 



% 



%** 




This publication has been cataloged as follows: 



Patten, Lowell L 

Preliminary testing of a prototype portable X-ray fluorescence 
spectrometer. 

(Bureau of Mines information circular ; 8888) 

Bibliography: p. 15-16. 

Supt. of Docs, no.: I 28.27:8888. 

1. Spectrometer, 2. Fluorescence spectroscopy. 3. X-ray spec- 
troscopy. I. Anderson, N. B. (Neal B.). II. Stevenson, J. J. (John 
J.). III. Title. IV. Series: Information circular (United States. Bu- 
reau of Mines) ; 8888. 

TN295.U4 [QC373.S7] 622s [622'. 13] 82-600159 AACR2 




/ CONTENTS 

<\J Page 

Abstract 1 

/K Introduction 2 

History 2 

Previous Bureau of Mines work 3 

Acknowledgments 3 

X-ray theory and its application to the portable spectrometer 3 

Instrument design and description 4 

Analytical procedures and results 6 

Laboratory testing 7 

Interference 9 

Matrix effect 11 

Summary of results 11 

Field testing 12 

Conclusions 14 

Recommendations 15 

Selected bibliography 15 

Appendix A. — Selected sections of PXRFS operation and maintenance manual 17 

Appendix B. — Tables of analytical results 24 

Appendix C. — Nuclear Regulatory Commission (NRC) licensing information 33 

ILLUSTRATIONS 

1. Characteristics of X-ray fluorescence spectra 4 

2. Portable X-ray fluorescence spectrometer (PXRFS) 5 

3 . PXRFS as used in the field 6 

4 . Periodic table of elements 8 

5. Sensor-head rack and pulverized sample in petri dish 9 

6. Spectra (CRT traces) of manganese ore and molybdenite 10 

7. Spectra (CRT traces) of erythrite and mercury ore 10 

8. Spectra (CRT traces) of samples containing iron, copper, calcium, and 
galena 10 

9. Spectra (CRT traces) of samples containing lead, zinc, and ferberite 10 

10. Spectra (CRT traces) illustrating interelement interference 11 

11. Calibration curves of five element standards having granitic matrixes.... 12 

12. High-impact plastic transport case for spectrometer 13 

13. Spectrometer in use on a mine dump 13 

14. Calibration spectrum of 109 Cd source under normal operating temperature 
and at 108° F 14 

A-l. Front panel and controls of PXRFS 17 

TABLES 






B-l. X-ray excitation capabilities of 55 Fe and 109 Cd for selected elements.... 24 
B-2. Comparison of minus 200-mesh pulp sample analysis data with PXRFS test 

results 25 

B-3. Comparison of USGS sample standards with PXRFS test results 31 

B-4. PXRFS analysis of selected Bureau of Mines mineral display specimens 32 






PRELIMINARY TESTING OF A PROTOTYPE PORTABLE X-RAY 
FLUORESCENCE SPECTROMETER 

By Lowell L. Patten, 1 Neal B. Anderson, 2 and John J. Stevenson 



ABSTRACT 

The Federal Bureau of Mines participated with the National Aeronautics 
and Space Administration and Martin Marietta Aerospace in developing, 
building, and testing a portable X-ray fluorescence spectrometer for use 
as an analyzer in mineral-resource investigative work. The prototype 
battery-powered spectrometer, measuring 11 by 12 by 5 inches and weigh- 
ing only about 15 pounds, was designed specifically for field use. The 
spectrometer has two gas-proportional counters and two radioactive 
sources, 109 Cd and 55 Fe. Preliminary field and laboratory tests on rock 
specimens and rock pulps have demonstrated the capability of the spec- 
trometer to detect 33 elements, to date. Characteristics of the sys- 
tem present some limitations, however, and further improvements are 
recommended. 



'Mining engineer (retired). 
^Geologist. 
All authors are with Intermountain Field 
Denver, Colo. 



Operations Center, Bureau of Mines, 



INTRODUCTION 



The principles of X-ray fluorescence 
spectrometry long have been known and 
studied intensively by numerous investi- 
gators (see bibliography). Laboratory 
model spectrometers have been available 
commercially for many years. The feasi- 
bility of a portable X-ray fluorescence 
spectrometer (PXRFS) was investigated in 
the 1960's, and several companies devel- 
oped portable analyzers, some using X-ray 
generators and others using radioactive 
isotope sources. In general, however, 
these analyzers were heavy, cumbersome, 
complex to use, and lacking in versatil- 
ity. Complications included the need to 
cool the X-ray generators, the use of 
filters to increase discrimination of the 
detectors, and the fact that most of 
these analyzers would detect only one or 
no more than a few elements at one time. 

An improved portable spectrometer would 
greatly facilitate the Federal Bureau of 
Mines mineral-land assessment work, would 
substantially assist mineral exploration 
work in general, and could benefit both 
Government and industry as an aid in min- 
eral identification and analysis. 

This report summarizes results of a 
twofold project to apply principles of 
X-ray fluorescence spectrometry to min- 
eral identification and element quantifi- 
cation. The first part of the project 
was to construct a portable, energy dis-> 
persive, X-ray fluorescence spectrometer. 
The second part was to test the prototype 
instrument in laboratory and field situa- 
tions to determine its operating charac- 
teristics, its response, and its useful- 
ness in mineral-resource investigative 
work. 

Instrument response was observed and 
recorded in the Planetary Geology Labora- 
tory of Martin Marietta Aerospace near 
Denver, Colo., in the Bureau's Inter- 
mountain Field Operations Center at the 
Denver (Colo.) Federal Center, in the 
mountains west of Denver, and near 
Tucson, Ariz. 



During testing, a limited effort was 
made to compare the PXRFS capabilities 
with those of emission spectrometers. 
The PXRFS can be used in conjunction 
with, but not as a substitute for, a 
laboratory emission spectrometer. 

History 

The idea of a spectrometer that could 
be carried easily in the field and could 
quickly identify and quantify many ele- 
ments with little or no sample prepara- 
tion only recently became technologically 
possible. 

In the 1970' s, Martin Marietta (MM), 
under contract with National Aeronautic 
and Space Administration (NASA), devel- 
oped a miniature X-ray fluorescence spec- 
trometer, which employed 55 Fe and 109 Cd 
isotopes as X-ray sources, for use on the 
Viking Project Mars Lander. 

The senior author of this report sug- 
gested that the Mars Lander technology 
might be followed in developing a porta- 
ble spectrometer that could be useful as 
a field instrument in mineral explora- 
tion. Subsequently, Bureau personnel 
consulted with representatives of MM and 
NASA, and in 1975 a contract was negoti- 
ated for developing and constructing a 
portable X-ray fluorescence spectrometer. 
The work was funded mostly by the Bureau 
and it also provided a list of elements 
of interest in mineral exploration. Sug- 
gestions for design to facilitate field 
and laboratory use were contributed by 
both the Bureau and NASA. 

The PXRFS was completed in mid-1980; 
subsequently, several minor adjustments 
and microprocessor program modifications 
were made. A testing program began in 
late 1980 and continued intermittently 
until the spring of 1981. A Nuclear Reg- 
ulatory Commission (NRC) licensing (see 
appendix C for license requirements) 
problem delayed transfer of the spectrom- 
eter custody from the contractor to the 



Bureau until July 1981 when the Bureau's 
source license was modified to include 
the PXRFS and its radioactive isotopes. 

Previous Bureau of Mines Work 

The Bureau of Mines has done consid- 
erable work in laboratory and field 



applications of X-ray fluorescence as 
shown by citations in the bibliography. 
Most of this research advanced the 
general technology but was directed 
mainly toward special applications, and, 
in particular, toward high quantitative 
accuracy in the laboratory. 



ACKNOWLEDGMENTS 



Those who technically contributed the 
most to the current project were 
Benton C. Clark, senior research scien- 
tist, and Ludwig Wolfert, staff engineer, 
both of Martin Marietta. Also instru- 
mental in the development of the PXRFS 



were Warren C. Kelliher, contract mana- 
ger, and Charles R. Eastwood, manager, 
environmental projects, both from NASA, 
and Sheldon P. Wimpfen, chief mining 
engineer, and Lee R. Rice, geologist, of 
the Bureau of Mines. 



X-RAY THEORY AND ITS APPLICATION TO THE PORTABLE SPECTROMETER 



X-rays can be generated by electrical 
apparatus or originate as gamma rays dur- 
ing the decay of radioactive isotopes of 
elements. The origin of characteristic 
X-ray fluorescence can briefly be 
described as follows: When sufficient 
energy is introduced into the atom, by 
X-rays or gamma rays, an electron is dis- 
placed from one of the inner shells. The 
atom is then in an excited (ionized) 
state. The place of the missing electron 
is filled immediately by an electron from 
a neighboring outer shell whose place, in 
turn, is filled by an electron from the 
next outer shell. The electron from a 
high energy level (outer shell) enters a 
lower energy level (inner shell), emit- 
ting excess energy in the form of X-ray 
fluorescence. 

Each element has a characteristic emis- 
sion energy for each electron shell, 



referred to as K, L, and M spectra (K- 
alpha, K-beta, etc.), indicating from 
which electron shell the fluorescence 
originates. Figure 1 illustrates these 
phenomena by showing the characteristic 
K, L, and M spectra and their correspond- 
ing energies (in kiloelectron volts, 
keV). 

An X-ray fluorescence spectrometer, 
then, is used to record these character- 
istic spectra and their energies, thereby 
identifying and possibly quantifying 
the elements. Four functions, therefore, 
were required in the PXRFS to accomplish 
this: (1) generate X-rays, (2) transform 
fluorescent energies into electrical 
impulses, (3) process, interpret, and 
store these electrical impulses, and 
(4) display the interpreted data in a 
form the operator could use. 



ATOMIC NUMBER 



ELEMENT 




20 
ENERGY (keV) 



FIGURE 1#- Characteri sties of X-ray fluorescence spec- 
tra. (Copyright, ASTM, 1916 Race Street, Philadelphia, 
Pa. 19103. Reprinted/adapted, with permission.) 



INSTRUMENT DESIGN AND DESCRIPTION 

Design objectives were to obtain an 
optimum combination of available technol- 
ogy and commercially available compo- 
nents, considering the factors of weight, 
size, operator training, speed of analy- 
sis, accuracy, versatility, and durabil- 
ity under field conditions. Within this 
philosophy, the optimum spectrometer 
design became a unit containing two X-ray 
sources (radioisotopes), in order to 
excite X-ray response from a wide range 
of elements, coupled with gas- 
proportional counters (detectors) that 
would feed electrical impulses (trans- 
formed fluorescent energies) to a micro- 
processor for processing, interpretation, 
and storage in memory; in turn, the 
microprocessor would feed data to a cath- 
ode ray tube (CRT) display and a liquid 
crystal display (LCD). 

The PXRFS was designed for operators 
trained in mineral identification but 
lacking extensive technical knowledge of 
spectroscopy. The operator needs con- 
siderable experience in using the PXRFS 
before he/she fully understands the 
displays. 

The PXRFS (fig. 2) consists of an ana- 
lyzer unit, including a microprocessor, 
solid-state circuitry, batteries (power 
source ranges from 7 to 40 volts DC) and 
a control panel with a 1.3- by 1-inch CRT 
display, a 0.75- by 3.75-inch alpha- 
numeric LCD, and a variety of switches 
and dials (described in appendix A), all 
connected to a sensor head by a 6-foot, 
spring-coiled cable. The sensor head 
contains two radioisotopes, 100 milli- 
curies (mCi) of 55 Fe having a calibration 
target composed of sulfur and titanium, 
and 15 mCi of 109 Cd having a calibration 
target composed of titanium and zir- 
conium, two collimators, and two gas- 
proportional counters. When its cable is 
unplugged, the sensor head can be stored 
in the lid of the analyzer unit. 

Dimensions of the PXRFS, lid closed, 
are about 11 by 12 by 5 inches (sen- 
sor head is 10.5 by 2.5 by 1.5 inches). 
The complete spectrometer weighs about 







FIGURE 2. - Portable X-ray fluorescence spectrometer (PXRFS). A, Maimanalyzer unit; B, sensor 
head. 



15 pounds and can be carried in the field 
by a shoulder harness (fig. 3) which 
allows the operator a good view of the 



displays and use of both hands 
trol manipulation. 



for con- 



ANALYTICAL PROCEDURES AND RESULTS 



Information gathered during the tests 

is preliminary and is presented here as a 

guide to prospective portable spectrom- 
eter users. 

Previous investigators (bibliography) 
have shown that factors having a signifi- 
cant influence on response include mois- 
ture, particle size, the geometric rela- 
tionship between the source, sample, and 
detector, and effects from surrounding 
elements ("matrix effect and interelement 
interference") . 



The useful response from elements in 
certain combinations varied considerably; 
consequently, the success of these deter- 
minations varied widely, as indicated in 
table B-l. 

Analytical procedure consisted of plac- 
ing a sample as close as practical to 
the sensor-head port, opening the port 
by sliding the port-shutter control 
knob (as described in appendix A), thus 
irradiating the sample; then the operator 
recorded the lapsed time of irradiation, 




FIGURE 3. - PXRFS as used in the field. 



total counts, elements detected, and the 
ratio values. The operator determines 
the length of analysis time by either 
presetting the time on the control panel 
or releasing the port-shutter control 
knob when a significant spectrum is dis- 
played on the CRT. The spectrum is then 
studied and sometimes photographed by the 
operator. 

The ratio value is derived by the 
microprocessor, and is a ratio between 
the fluorescent intensity (counts) of the 
element being measured and the back- 
scatter (BS) peak intensity, a process 
intended to compensate automatically for 
sample grain size and the geometry of the 
source, sample, and detector. The BS 
peak is created by radioisotope X-rays 
that escape the fluorescence process, 
that is, reflected X-rays recorded by the 
detector and displayed as a peak at the 
high-energy end of the spectrum. 

Laboratory Testing 

Theoretically, 73 elements can be 
detected by the PXRFS tested by the 
Bureau (fig. 4A) . However, as of this 
writing, only 33 elements have been 
detected, as shown in figure 4B. This is 
attributable in part to a lack of speci- 
mens or standards that contain the other 
elements. Moreover, the precious metals 
were not detected, owing partly to the 
lack of spectrometer sensitivity to low 
concentrations of precious metals nor- 
mally found in natural occurrences and 
partly because the 109 Cd isotope decays 



to silver and does not 
cence from silver atoms. 



excite fluores- 



The PXRFS response 
(secondary X-ray emiss 
was investigated on 52 
7 control standards 
Barton of the U.S. 
(USGS), Denver, Colo., 
display specimens, and 
pies previously analyz 
Indian-lands project 
through B-4) . 



to fluorescence 
ions) of elements 

samples including 
loaned by Harlan 
Geological Survey 

13 Bureau mineral 
32 pulverized sam- 
ed for a Bureau 
(see tables B-2 



Pulverized samples were poured into 
plastic 35-mm-diameter by 10-mm-deep 
petri dishes. Each dish was filled to 
heaping, tamped lightly for compaction, 
and leveled with a knife or straightedge, 
which provided a smooth sample surface 
for X-ray analysis. The petri dish was 
placed in a sample receptable in the base 
of a sensor-head rack (fig. 5), which has 
corner uprights designed to support the 
sensor head at an optimum analysis dis- 
tance and position over the pulverized 
sample. 

Pulverized samples in standard kraft 
paper envelopes were analyzed without 
removal from the envelopes. The response 
from the 55 Fe source was not usable 
because the envelope blocked the second- 
ary, or perhaps, the primary X-rays; 
response from the 109 Cd source appeared 
normal. This rapid method of analysis 
may effectively identify the composition 
of pulverized samples without removing 
them from the envelopes. 




H 



Li 

Hi - 
Na 



Tt- 



Be 

Mg 



30 

Ca 



21 



Sc 



32 

Tl 



23 



24 

Cr 



25 

Mn 



26 

Fe 



27 

Co 



28 

Ni 



29 

Cu 



30 

Zn 



B 

TC 
Al 



31 

Ga 



14 



Si 

32 

Ge 



N 



W 



33 

As 



16 



34 

Se 



CI 



35 

Br 



He 

Tor 1 
Ne 

if 1 - 
Ar 



36 

Kr 



[37 

Rb 



3T - 

Sr 



39 



40 



41 



Zr 



Nb 



42 

Mo 



43 

Tc 



44 

Ru 



45 

Rh 



46 

Pd 



47 

Ag 



48 

Cd 



49~ 



In 



50 - 

Sn 



5T 



Sb 



56 

Ba 



52 

Te 

if*- 
Po 



w 



Xe 



55 

Ca 



La 



72 



Hf 



73 

Ta 



74 

w 



75 

Re 



76 
08 



77 



lr 



7T~" 

Pt 



7r~ 
Au 



80 

Hg 



81 

Tl 



82 

Pb 



w 



Bl 



85 

At 



86— 

Rn 



[p - 
Fr 



ii — 

Ra 



Ac 



** 



58 

Ce 



90 

Th 



59 



Pr 



91 



Pa 



60 

Nd 



92 



u 



61 

Pm 



93 



Np 



62 

Sm 



94 
Pu 



63 

Eu 



95 
Am 



64 

Gd 



96 

Cm 



65 

Tb 



97 
Bk 



66 

Dy 



98 

Cf 



67 

Ho 



99 



Es 



68 



Er 



100 
Fm 



69 

Tm 



101 
Md 



70 

Yb 



102 
No 



71 



Lu 



103 

Lr 



H 



Li 



[Tl 

Na 



w 



[37 
Rb 



Be 



T5 

Mg 



» — 
Ca 



Sr 



B 



21 



Sc 



39 



22 
Tl 



40 



23 



41 



Nb 



24 

Cr 



42 

Mo 



25 

Mn 

■11 



43 



Tc 



26 

Fe 



44 
Ru 



27 

Co 



45 



Rh 



28 

Ni 



46 

Pd 



29 

Cu 



47 
Ag 



30 

Zn 



48 

Cd 



B 



13 

Al 



31 

Ga 



VIA VII* 



49 



In 



14 



Si 

32 

Ge 



50 

Sn 



N 



15 



33 

As 



51 



Sb 



16 



34 

Se 



52 

Te 



IT - 

CI 



35 

Br 



53 



He 



10 
Ne 



Ar 



36 

Kr 



54 
Xe 



55 

Cs 



56 

Ba 



57 * 
La 



72 



Hf 



73 
Ta 



74 



W 



75 
Re 



76 



77 



Os 



lr 



78 
Pt 



79 

Au 



Hg 



81 

Tl 



82 

Pb 



83 

Bi 



54 

Po 



85 

At 



86 

Rn 



87 

Fr 



88 

Ra 



89 ** 

Ac 



• 


58 

Ce 


59 
Pr 


60 

Nd 


61 

Pm 


62 

Sm 


63 

Eu 


64 

Gd 


65 

Tb 


66 

Dy 


67 

Ho 


68 

Er 


69 

Tm 


70 

Yb 


71 

Lu 


r* 


90 

Th 


91 

Pa 


92 

u 


93 
Np 


94 
Pu 

M— ■*■■ 


95 

Am 


96 

Cm 


97 
Bk 


98 

Cf 


99 
Es 


100 
Fm 


101 
Md 


102 
No 


103 

Lr 



FIGURE 4. - Periodic table of elements. Shaded areas show A, elements theoretically 
detectable by PXRFS; B, elements actually detected in Bureau of Mines 
tests. 




FIGURE 5. - Sensor-head rack and pulverized sample in petri dish. 



Figures 6 through 9 are spectral traces 
from photographs of the CRT display. 
Each figure shows the response of certain 
elements or minerals. These spectral 
traces illustrate the fluorescent inten- 
sity (counts) plotted in relation to the 
element emission energies as interpreted 
by the PXRFS microprocessor. Shown are 
the element X-ray emission peaks and 
their spectral line classifications and 
the position of element emissions rela- 
tive to backscatter emissions. 



Interference 

Because X-ray emission energies (kilo- 
electron volts) of many elements (fig. 1) 
are close in value, and because the PXRFS 
uses a proportional counter as a detec- 
tor, fine resolution of the element emis- 
sion energies was difficult. The pro- 
blem was interference between elements, 
recorded as distortions of spectra. 



10 



Mn K-alpha 




BS 



Energy 




Energy 



FIGURE 6. - Spectra (CRT traces) of A, man- 
ganese ore and B, molybdenite 
(T°9Cd source). 



Co K-alpha 

\ At K-alpha 




BS 



Energy 



Hg L-alpha 

\ Hg L-beta 
Ca K-alpha /\ / 

Fe K-alpha 




Energy 



FIGURE 7. - Spectra (CRT traces) of A, 
erythrite and B, mercury ore 
(10'Cd source). 



Fe K-alpha 




BS 

I 



Energy 



Pb L-alpha 



Pb L-beta 




BS 



Energy 



FIGURE 8. - Spectra (CRT traces) of A, sam- 
ple containing iron, copper, and calcium, 
and B, galena ( 109 Cd source). 





, 






J 
; 


Pb L-alpha 
/ 
Zn K-alpha A p b L-beta 

i / \ 


BS 

i 


A 






nergy 




i 


W L-alpha 

1 W L-beta 
1 • 

„ Fe K-alpha / \ 
i /\J \ 

i / \ 






s 

J 


BS 

i 












1 



FIGURE 9. - Spectra (CRT traces) of A, sam- 
ple containing lead and zinc and B, fer- 
berite ( 109 Cd source). 



11 



Figure 10A is a spectral trace from a 
pulverized sample of a quartz vein in 
granite, which chemical analysis indi- 
cated to contain 23.7% As, 5.2% Cu, and 
3.05% Pb. This spectral trace illus- 
trates the interference created when cop- 
per, iron, and arsenic occur together. 
The copper emissions were interpreted as 
having an additive effect to the area of 
the spectrum between the iron and arsenic 
emission peaks. Also, the arsenic emis- 
sions appear to mask the lead responses; 
however, lead emissions have an additive 
effect on the arsenic emission peak. 
Figure 10B, a spectral trace of a pulver- 
ized sample of galena in an igneous rock, 
which contains 1.32% Pb and 1.95% Zn, 
illustrates further the interference 
problem by showing the distortion of the 
predominant iron emission peak by the 
lead and zinc emissions. 



At K-alpha 

/ 



Cu ? K-alpha 
Fe K-alpha 




BS 

I 



Energy 



11 CRT overlap ->. 




JM 


Fa K-alpha 




1 Zn K-alpha 


Ca K-alpha f 


W 


* ^ 


\ Pb L-alpha 


S S K-alpha / 

i \J 


\/ Pb L- 



beta 



BS 



Energy 



B 



FIGURE 10. - Spectra (CRT traces) illustrating inter- 
element interference. A, Sample containing As, 
Cu, Pb, and Fe; B, high-Fe sample containing 
Zn and Pb (lO'cd source). 



Iron was the most significant source of 
interference, owing to its natural abun- 
dance and strong X-ray emission response. 
Many elements of economic interest occur 
with iron; because iron interfered with 
the X-ray responses of these elements, 
iron interference became the major prob- 
lem. In tests on certain clays (ceramic 
raw materials) even minor amounts of iron 
impurities were detected; the PXRFS could 
be used for the selection of low-iron 
clays for industrial purposes. 

With experience, the PXRFS operator was 
able to recognize characteristic emission 
peaks of elements even though the peaks 
were modified by interference. 

Matrix Effect 

The matrix effect is a form of inter- 
ference simply defined as the effect 
matrix elements have on the X-ray 
response of other elements. Matrix 
effect is due to an interaction between 
the emission and absorption characteris- 
tics of the matrix elements and the emis- 
sion energies (or wavelengths) of the 
elements being analyzed. 

Rock-forming or gangue minerals (ma- 
trix) can have a significant effect on 
the X-ray responses from elements of 
possible economic interest. If rock com- 
position changes, the matrix effect also 
changes. That is, as the relative pro- 
portion of matrix elements changes, their 
effect on economic elements changes 
in the form of an increase or decrease 
in secondary radiations or emission 
absorptions. 

Summary of Results 

Positive identification and semiquanti- 
tative analyses of elements were possible 
for many of the samples tested. The lim- 
itations created by the detection system 
used in the PXRFS, however, precluded 
utilization of the instrument's full 
potential. 

Element identification was possible 
for most of the elements tested and was 



12 



affected only by the presence of inter- 
fering elements for element concentra- 
tions less than 0.10%. 

Quantitative analyses were hindered by 
both interelement interference and matrix 
effect, the matrix effect especially 
affecting the results when element con- 
centrations were low (generally less than 
0.10%). Semiquantitative results proba- 
bly can be obtained by use of the PXRFS, 
but it will be necessary to use samples 
(standards) that have known but varying 
percentages of element concentration for 
comparison with samples of unknown com- 
position. Five element calibration 
curves (fig. 11), constructed from USGS 
standardized samples, are plots of ele- 
ment concentrations relative to the ratio 
values calculated by the PXRFS. Quanti- 
fication of elements in a sample of 
unknown composition can be estimated by 
using calibration curves if the composi- 
tion of the sample approximates that, of 
the standards used to make the calibra- 
tion curves. 

The overall quantification results, 
based on spectral emission data as com- 
pared to analyses of the samples, varied 
from useful to nearly useless, depending 
on the relative percentages of interfer- 
ing elements as well as the X-ray 
response characteristics of a particular 
element and those elements adjacent to it 
in the spectrum. 

Field Testing 

On short field trips to selected mining 
districts west of Denver, Colo. , and on 
a field trip to southwestern Arizona, 
the PXRFS was tested for its durability 
and its practicability in addition to 
its analytical accuracy and response 
capabilities. 

The PXRFS was transported in a four- 
wheel-drive vehicle to selected test 
sites over varying types of roads. Dur- 
ing transportation, the instrument was 
carried in a high-impact plastic case 
(fig. 12). 

Hand specimens collected from outcrops 
or mine dumps and outcrop faces were 



analyzed during the field tests 
(fig. 13). Some hand specimens and out- 
crop faces were difficult to analyze with 
the PXRFS because of their surface irreg- 
ularities. One-handed operation of the 
sensor head during field tests while 
climbing on rock outcrops proved to be 
difficult because of the sensor head 
shape and the tension on the port shutter 
control return spring. 







RATIO (element to backscatter) 

FIGURE 11.- Calibration curves of five element 
standards having granitic matrixes. 



13 




FIGURE 12. - High-impact plastic transport case for spectrometer. 



jff-i ; . • 





FIGURE 13. - Spectrometer in use on a mine dump. 



14 



The PXRFS response was compared 
with visual, physical, and chemical 
mineral-identification techniques; sider- 
ite, sphalerite, ferberite, and powellite 
were among the minerals identified during 
the field tests. 

The tests disclosed that air tempera- 
tures between 50° and 90° F had little 
effect on the PXRFS; however, the instru- 
ment did undergo a spectral shift toward 
the low-energy end of the spectrum at 
108° F. Figure 14A shows the 1 ° 9 Cd cali- 
bration spectrum (trace) produced by the 
PXRFS within the operating temperature 
range; figure 14B^ illustrates the spec- 
tral shift that occurs to the same cali- 
bration spectrum at 108° F. At air tem- 
peratures less than 50° F, the spectrum 
appeared to shift slightly toward the 
high-energy end of the spectrum. The 
spectral shift phenomenon made element 
identification difficult and necessitated 
calibration adjustments in the sensor 
head that were time consuming and not 
always successful. 

Durability of the PXRFS was somewhat 
less than expected. A fuse holder 
attached to the chassis broke loose; 
wires in the sensor head broke twice from 
flexure; a beryllium window in the 109cd_ 
coupled detector shattered, which made 
the detector and the PXRFS inoperable; 



Calibration cursors 




Energy 



Calibration cursors 




Energy 



FIGURE 14. - Calibration spectrum of 109 Cd source. 

A, under normal operating temperature; 

B, at 108° F. 

and the analyzer unit lid hinges were 
sprung from the weight of the sensor 
head. 



CONCLUSIONS 



This project involved limited testing 
of the PXRFS for field use in mineral- 
resource investigative work, and results 
presented in this report should be con- 
sidered preliminary. Testing demon- 
strated a portion of the capabilities and 
limitations of the spectrometer in min- 
eral identifications and quantitative 
determinations. 

The advantages of the PXRFS are (1) it 
is portable and can be carried in the 
field with little difficulty, (2) it has 
repeat analysis capabilities, (3) analy- 
sis time is generally less than 1 minute 
(if the radioisotopes have not undergone 
a decay of one half-life), (4) all data 
are available instantly on the displays, 



(5) no sample preparation is necessary in 
the field, and (6) it is relatively main- 
tenance free. 

Limitations of the PXRFS are (1) poor 
resolution of emission data owing to use 
of a gas-proportional detector that 
causes interference problems, (2) short 
half-life ( 109 Cd = 1.2 years, and 55 Fe 
= 2.6 years) of the radioisotopes results 
in periodic replacement expense, (3) dur- 
ability is somewhat less than expected, 
(4) the calibration adjustment screws, 
located in one end of the sensor head, 
are relatively inaccessible, (5) spectral 
shifts occur when the PXRFS is operated 
in air temperatures less than 50° F or 
more than 90° F, (6) the CRT display is 



15 



hard to read because of its miniature 
size, or because of bright daylight in 
the field, and (7) one-handed operation 
of the sensor head is difficult because 
of its shape and port shutter control 
spring tension. 



At this time the PXRFS falls short 
in achieving the desired objective 
of reliable quantitative analytical 
results. 



RECOMMENDATIONS 



Recommendations for modification of the 
PXRFS mainly involve the detectors and 
the radioactive sources. In order to 
improve spectral resolution and reduce 
operating expenses of the PXRFS, the fol- 
lowing modifications are suggested: 

1. Replace the gas-proportional coun- 
ters with a single mercuric iodide detec- 
tor to enhance spectral resolution. 

2. Replace the 1 ° 9 Cd and 55 Fe radio- 
isotopes with an americium ( 24 1 Am) 
source, thereby increasing the element 
excitation range and reducing isotope 
replacement costs (the 241 Am source has a 
half-life of 458 years). 



A miniature X-ray generator may be an 
alternative to radioactive isotopes as an 
X-radiation source. 



Other modifications to the 
special-use purposes (such 
trol sampling) and to further 
and complexity, might include 
ing: Use only one radioact 
test a weaker radioactive 
lower cost); eliminate the 
use a three- or four-digit 
manual element selector (cu 
in present PXRFS) with a me 
readout. 



PXRFS, for 
as ore con- 
reduce cost 
the follow- 
ive source; 
source (at 
CRT display; 
LCD and a 
rsor control 
ter (analog) 



SELECTED BIBLIOGRAPHY 



1. Bearden, J. A. X-Ray Wavelengths 
and X-Ray Atomic Energy Levels. National 
Bureau of Standards Reference Data Series 
No. 14, 1967, 66 pp. 

2. Bertin, E. P. Principles and Prac- 
tice of X-Ray Spectrometric Analysis. 
Plenum Press, New York, 2d ed. , 1975, 
1079 pp. 

3. Birks, L. S. X-Ray Spectrochemical 
Analysis. Wiley Interscience, New York, 
2d ed. , 1969, 143 pp. 

4. Burkhalter, P. G. , and W. J. Camp- 
bell. Comparison of Detectors for Iso- 
topic X-Ray Analyzers. Proc. 2d Symp. 
Low Energy X- and Gamma Sources and 
Applications, University of Texas, Aus- 
tin, Tex., Mar. 27-29, 1967, ORNL-IIC-10, 
pp. 393-423. 

5. Campbell, W. J. Application of 
Radioisotopes in X-Ray Spectrography. 
Ch. in Radiation Engineering in 
the Academic Curriculum. International 



Atomic Energy 
pp. 225-258. 



Agency, Vienna, 1975, 



6. Campbell, W. J. Energy Dispersion 
X-Ray Analysis Using Radioactive Sources. 
In X-Ray and Electron Methods of Analy- 
sis, ed. by H. Van Olphen and W. Parrish 
(Progress in Analytical Chemistry Series: 
v. 1). Plenum Press, New York, March 
1968, pp. 36-54. 

7. Campbell, W. J., and J. V. 
Gilfrich. X-Ray Absorption and Emission. 
Anal. Chem. Ann. Rev., v. 42, No. 5, 
April 1970, pp. 248R-268R. 

8. Clark, B. C, and A. K. Baird. 
Martian Regolith X-Ray Analyzer: Test 
Results of Geochemical Performance. 
Geology, v. 1, No. 1, September 1973, 
pp. 15-17. 

9. Hurlbut, C. S., Jr. Dana's Manual 
of Mineralogy. John Wiley & Sons, Inc., 
New York, 17th ed. , 1959, 609 pp. 



lo 



10. Jenkins, R., and J. L. DeVries. 
Practical X-Ray Spectrometry. Springer- 
Verlag, New York, 2d ed. , 1969, 180 pp. 

11. Muller, R. 0. Spectrochemical 
Analysis by X-Ray Fluorescence. Plenum 
Press, New York, 1972, 326 pp. 



Electron Probe Analysis. ASTM Special 
Tech. Pub. 485, 1971, 285 pp. 

14. Thatcher, J. W. , and W. J. Camp- 
bell. Fluorescent X-Ray Spectrographic 
Probe — Design and Applications. BuMines 
RI 5500, 1959, 23 pp. 



12. Nuffield, E. W. X-Ray Diffraction 
Methods. John Wiley & Sons, New York, 
1966, 406 pp. 

13. Russ, J. C. (coordinator). Energy 
Dispersion X-Ray Analysis: X-Ray and 



15. 



Instrumentation for Pri- 



mary and Secondary Excitation of Low 
Energy X-Ray Spectral Lines. BuMines 
RI 6689, 1965, 29 pp. 



17 



APPENDIX A.— SELECTED SECTIONS OF PXRFS OPERATION 

AND MAINTENANCE MANUAL 1 

Figure A-l provides a display of the front panel and controls of the PXRFS as a 
reference for the instructions contained in this section. 



CRT display^ Calibration switch^ /Memory switch /Liquid crystal display 




'CRT intensity control 
'Cursor potentiometer 

FIGURE A-l. - Front panel and controls of PXRFS. 



Count range 
switch 



Element-count- 
ratio switch 



iMartin Marietta Corp., rev. July 11, 1980. 



18 

OPERATING INSTRUCTIONS 

1 . Power on 

A. Connect sensor head to instrument by pushing the sensor head cable connector 
onto the face panel connector (aline before plugging in) and then turning 
clockwise for approximately one-third turn. 

B. Turn the COUNT RANGE switch to any of its numbered positions (typically to 
the 250 position). 

C. Set the SECONDS switch to 30. 

D. The liquid crystal display (LCD) shows the results of the instrument auto- 
matic self-test. It will display either "SELF TEST PASSED" or a combination 
of warning messages. 

E. The next message is the name and revision level of the software program 
stored in the PXRFS microcomputer. 

F. The LCD will now continuously repeat "WAITING FOR OPEN SHUTTER OR CAL SWITCH" 
until one or the other of these actions is taken. 

2. Sleep Mode 

A. If no switch positions are changed for approximately 2 minutes, the unit will 
switch to a low-power mode, and the LCD will display "ASLEEP." The CRT and 
other high power circuits are powered off. Memory data are retained. 

B. To resume operation, toggle the ELEMENT-COUNT-RATIO switch. The unit will 
wake up with the same status as when it went to sleep. 

3. Calibration Mode 

A. Calibration should be performed before starting a new series of analyses. 

B. After the power-on step, with the LCD repeating the "WAITING..." message, set 
the SECONDS switch to either COUNTS or to one of the numbered seconds 
positions. 

C. Set COUNT RANGE switch to desired scale (typically 250 for calibration). 

D. Verify sensor head shutter is closed. 

E. Toggle CAL switch momentarily to LO. LCD displays "Fe-55" for 2 seconds, 
then begins displaying elapsed analysis time as the spectrum is accumulated. 

F. The unit is now analyzing the Fe-55 calibration sample (sulfur and titanium 
target) built into the sensor head. 

G. Adjust CRT focus and intensity knobs for best viewing of the spectrum. 

H. When analysis is complete the LCD will display "CAL," and the CRT display 
will be continuous with two flashing cursors. The left cursor marks where 
the sulfur peak should appear, and the right cursor where the titanium peak 
should appear. 



19 



NOTE: At any time during or after analysis the COUNT RANGE switch may be 
used as desired to adjust the vertical expansion of the spectrum on 
the CRT display. 

I. If the cursors are not on the two peaks, adjust the LO trimpot on the sensor 
head and repeat the analysis as necessary. After adjusting the poten- 
tiometer, restart the spectrum by operating the CAL switch again. 

J. After the Fe-55 channel is calibrated, repeat the above procedure for Cd-109. 
Substitute CAL HI for CAL LO and use the HI trimpot on the sensor head. For 
Cd-109 the left cursor marks titanium and the right cursor marks zirconium. 

4. Normal Operation 

A. After power-on and calibration steps, the unit is ready to analyze samples. 

B. To analyze, adjust the SECONDS and COUNT RANGE switches for the desired type 
of analysis. Set the MEMORY switch to either A or B, depending upon which 
half of memory the spectrum is to be stored. Use the A and B setting only if 
there is no need to compare two different spectra. 

C. Place the sensor head port against the sample of interest. If this is not 
possible, place the port as close to the sample as possible (see "Safety" 
section at the end of the appendix) . 

D. Using an index finger, press and hold the shutter control either forward for 
a Cd-109 analysis, or backward for an Fe-55 analysis. The LCD will first 
identify which radiation source is in use and then the elapsed analysis time 
(in seconds). The beeper in the sensor head will sound to warn that a radio- 
active source is exposed through the open shutter. 

NOTE: If the beeper doesn't sound when the shutter is opened, notify the 
instrument manufacturer. 

E. While waiting for the analysis to complete, observe the spectrum building up 
on the CRT. When sufficient data have been taken, release the shutter con- 
trol. Verify that the alinement circle is properly centered in the port win- 
dow, indicating the spring-loaded shutter is in the fully closed position. 

F. The COUNT RANGE switch may be used to expand the CRT display as desired. 

CAUTION: Do not turn the COUNT RANGE switch to the 9 o'clock position, or 
the unit will be powered off and special data lost.) 

G. To identify a peak, use the CURSOR knob to adjust the bright dot to the top 
of the peak of interest. When the cursor is adjusted to an element channel, 
it will flash once per second, and with the ELEMENT-COUNT-RATIO switch set to 
ELEMENT, the LCD will display the element's chemical symbol. 

H. For a hard-copy record of the spectrum, connect the plot or tape output wires 
to a chart recorder or tape recorder, respectively. These wires are availa- 
ble from the connector at the front panel end of the sensor cable. 



20 



1. For a plot, set the SECONDS switch to PLOT. The LCD will display "PLOT 
REQUESTED" and "PLOT." When the "PLOT" message appears the unit will 
begin outputting 0- to -5-volt analog signals of spectral data at eight 
channels per second. The spectrum will repeat as long as the SECONDS 
switch is left on plot. Switching off the PLOT position at any time will 
terminate the output and return the spectrometer to the previous mode. 

2. For recording the spectrum onto magnetic tape, connect the tape output 
plug to the auxiliary or microphone input of a recorder. 

NOTE: It may be necessary to adjust the drive circuit output impedance 
to match the recorder input impedance. Turning the TAPE trimpot, 
on the INTERFACE printed circuit board, clockwise will increase 
the impedance to 60 kilohms maximum; turning counter-clockwise 
will decrease it to its 10-kilohm minimum. 

Set the COUNT RANGE switch to TAPE and then put the recorded in 
the record mode. . The LCD will display "TAPE DUMP REQUESTED" and 
"RECORD" (signals start of dump). The spectrum will be dumped 
only once, and the dump is not interruptable (takes approximately 
2 minutes). 

I. To perform more analyses, either leave the MEMORY switch in the same position 
it was, or change from A to B or from B to A to save the last spectrum taken. 
Repeat the steps under section 4. 

5. Charging the Batteries 

A. Be sure the COUNT RANGE switch is in the power-off position. 

B. Unplug sensor head cable by twisting counter-clockwise for approximately one- 
third turn and pulling to disengage. 

C. Plug in cable from the charging unit to the front panel connector. 

D. Place the CHARGE switch on the charging unit to one of its three positions. 
Under standard conditions, the unit contains nickel-cadmium batteries, but 
lead-acid may also be installed. Use L0 RATE for nickel-cadmium batteries if 
the time available for charging is 16 hours or more; if a fast charge is 
needed, or if the unit is to be operated during charging, use the HI RATE 
setting. 

E. Connect the appropriate terminals to either the 110-volt-ac source, or auto- 
motive battery (12 volts dc). 

ROUTINE MAINTENANCE 
1. Changing Sensor Heads 

A. Place the COUNT RANGE switch in the power-off position. 

B. Unplug sensor head at the front panel connector of the main unit by twisting 
counter-clockwise for one-third turn and pulling off. 

C. Plug in new sensor by alining connector, pushing to mate pins, and rotating 
connector clockwise to snap into locking position. 



21 



2. Changing the Desiccant Tube 

A. Replace or rejuvenate desiccant whenever the 60% sector changes from its nor- 
mal blue color to either pale pink or white. 

B. Remove the cartridge from the front panel by unscrewing it with fingers or a 
suitable straightedge. 

C. Screw in new unit, or rejuvenate removed cartridge by baking in an oven at 
125° C (257° F) for 2 hours or more. 

3. Replacing the Batteries 

The unit is powered by seven D-size batteries. Either rechargeable batteries 
(for example, nickel-cadmium or lead-acid cells) or nonrechargeable cells (for exam- 
ple, carbon-zinc, mercury, or lithium types) may be used. Standard rechargeable bat- 
teries are of the nickel-cadmium type, but the lead-acid type is preferred for opera- 
tion in very cold weather. 

A. Turn power off and unplug the sensor head. Remove the hinged lid (optional). 

B. Unscrew and remove the four mounting feet at the base of the instrument. 

C. Carefully place the unit on the side where the four mounts were removed 
(front panel facing up). 

D. Lift up on the front panel to pull the unit slowly out of the housing 
(assistance from a second person will be helpful and is a sensible 
precaution) . 

E. Set the unit down on a smooth surface. 

F. Note the battery orientations. All cells are alined in the same direction, 
with negative terminals closer to the CRT than the positive terminals. 

G. Remove batteries from holders by pushing end clips toward each other, and re- 
leasing tiedown clip with a slight twisting motion. 

H. Place new battery in proper direction and again press end clips inward to 
facilitate installing the tiedown clip in its original orientation. 

I. Replace one or more batteries as required. 

J. Carefully place unit in housing, aline holes at bottom with ports, and screw 
in mounting feet. 

TROUBLESHOOTING 

The first thing to suspect in the event of improper operation of the unit is a weak 
or dead battery. Even when the unit is powered by an external electrical source, a 
malfunctioning cell can prevent proper operation. Therefore, first try changing the 
batteries (see step 3 of the "Routine Maintenance" section) to verify that is not the 
problem. During this operation, check for any obvious internal problems: a printed 
circuit board that is not seated into its connector, a broken wire, dirt or other 
contamination in critical locations, charred or burned spots, etc. 



:: 



If this does not solve the problem, and the unit is known to have been exposed 
to high humidity or low temperatures, remove the desiccant tube and place the entire 
unit in a dry, warm environment to remove condensation. Replace the tube with a 
fresh or rejuvenated desiccant. 

In the case that the calibration peaks do not line up properly and cannot be 
adjusted into position with the appropriate potentiometer, the unit will require 
resetting by the manufacturer. However, it is possible to make temporary use of the 
instrument for field purposes by using the calibration targets built into the lid to 
note the channel numbers into which the elements of interest fall. With this 
approach, the operator must disregard the element symbols given on the LCD since 
these peaks will now occur slightly upscale or downscale from the normal position. 

SAFETY 

The PXRFS instrument has been engineered with every consideration for safety. A 
number of special features are designed to minimize the possible risks to the opera- 
tor and bystanders. It is extremely important, however, that all persons who are 
using, or have plans to use this instrument, read this section very carefully. THIS 
UNIT CONTAINS RADIOACTIVE MATERIALS and although these sources emit relatively low 
energy X-rays, and are carefully shielded, there is the possibility of unnecessary 
radiation exposure whenever the shutter is opened without the sensor head being 
placed flush against a suitable thick sample. 

1 . Radiation Hazard 

The standard sensor head contains two radioactive materials: approximately 100 mCi 
of iron-55 isotope and 15 mCi of cadmium-109. These sources are electroplated onto a 
substrate and then hermetically sealed into a rugged holder. The possibility of 
leakage of radioactive material is extremely remote. The sources are in turn mounted 
in shielded collimators. When in the neutral closed position the safety shutter pro- 
vides additional shielding to prevent any radiation from penetrating outside the sen- 
sor head. There is no hazard associated with handling or being near the sensor head 
when the shutter is closed (that is, when neither source is exposed). Of course, the 
sensor head should be kept secured from access by casual bystanders at all times. 

During acquisition of a spectrum, one or, the other of the two sources must neces- 
sarily be positioned to irradiate the samples with X-rays. To prevent unnecessary 
exposure to the operator and for maximum safety, the following rules must be 
followed: 

A. Always place the sensor head analysis port up against the sample before opening 
the shutter. 

B. If the sample surface is irregular or it is impractical to place the sen- 
sor head totally against the sample, be sure to position your hands, limbs, 
and body such that they are behind the sensor head. 

C. Never look at or handle the port window, except when the shutter is fully 
closed. 

D. If the warning beeper fails to operate when the shutter is opened, return the 
unit to the manufacturer. 



23 



E. Never attempt to repair or disassemble the sensor head. The only exception is 
simple replacement of the plastic film port window using a pre-prepared window 
kit. Make sure the shutter is in the neutral closed position before making 
this change. 

F. Insure that the radiation sources are leak checked at required intervals (typi- 
cally, every 6 months). 

G. Have available a thin-window Geiger counter or other radiation monitoring 
device. Periodically check the radiation level during normal operation to make 
sure unsafe procedures are not being followed. 

2. Shock Hazard 

All circuits within the PXRFS sensor head operate at low voltages, with the excep- 
tion of the detector bias supply. This supply provides 1,000 to 1,500 volts 
for operation of the proportional counters. Because this supply is potted, shielded 
by a metal housing, and contains a current-limiting resistor, the possibility of a 
malfunction causing serious shock is minimal. In the event of any indications of 
electronic problems within the sensor head, the unit should be returned to the 
manufacturer. 

An additional high voltage circuit is located within the main unit to provide the 
electron beam accelerating voltage for CRT operation. Because of this supply, it is 
recommended the unit never be turned to power-on condition when removed from its 
housing — for example, during a battery change-out operation. 



:4 



APPENDIX B. —TABLES OF ANALYTICAL RESULTS 
TABLE B-l. - X-ray excitation capabilities of 5 ^¥e and 1 09 Cd for selected elements 



Element 



X-ray source used 

in analysis 

55 Fe 

55 F e 

55Fe and 109 C d 

55Fe and !09cd 

109 C d 

109 Gd 

109 Cd 

109 C d 

55pe 

109 Cd 

109 C d 

109 Cd 

10? Cd 

109 C d 

55 Fe and 109 Cd 

55Fe and 109 Cd 

5 5Fe and 109cd. ... 

109 C d 

109 Cd 

55Fe and 109cd 

109 Cd 

109 Cd 



Source excitation 
capabilities 

Fair 

Good 

Fair 

Good 

Good 

Good 

Good 

Good 

Fair 

Good 

Fair 

Good 

Good 

Fair 

Fair 

Fair 

Good 

Good 

Fair 

Fair 

Good 

Good 



Most likely interfering 
elements 



Aluminum. . . 
Arsenic. . . , 
Calcium. . . . 
Chromium. . , 

Cobalt 

Copper. 

Iron , 

Lead 

Magnesium. , 
Manganese. . 
Mercury. . . , 
Molybdenum, 
Nickel. 
Niobium. . . , 
Silicon. . . , 
Sulfur...., 
Titanium. . , 
Tungsten. . , 
Uranium. . . 
Vanadium. . 

Zinc 

Zirconium. , 



Mg, 

Pb, 

K 

Fe, 

Mn, 

Fe, 

Cr, 

As 

Na, 

Cr, 

As, 

Nb, 

Cu, 

Th, 

Al 

K 

Ca, 

Cu, 

Mo, 

Ti, 

Cu, 

Th, 



Si 

Se, Hg 

V, Mn 

Fe, Ni, Cu 
Co. Ni, Zn 
Mn, Co, Ni, Cu 

Al 

Fe 

Pb 

U 

Co, Fe 

U 



V 

Zn 

Th, Sr, Nb 

Cr, Mn 

W 
Nb 



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31 



TABLE B-3. - Comparison of USGS sample standards 1 with PXRFS test results 
(Ratio value: Total counts divided by backscatter) 





Sample 
analysis, 


PXRFS test results 2 


Element 


Sample 
analysis, 


PXRFS test results 2 


Element 


Total 


Ratio 


Total 


Ratio 




% 


counts 






% 


counts 




Copper. . . 


0.01 


21 


0.125 


Rubidium. 


0.010 


6 


0.062 




.01 


25 


.125 




.021 


16 


.062 




.05 


30 


.125 




.046 


18 


.187 




.10 


25 


.187 




.100 


31 


.250 




.20 


54 


.312 




.215 


73 


.625 




.50 


92 


.625 




.464 


116 


1.187 




1.00 


130 


1.000 












2.00 


301 


2.312 


Strontium 


.001 


10 







5.00 


945 


9.062 




.010 
.021 


13 
12 



.062 




.046 


18 


.062 




.046 


13 


.125 




.100 


20 


.125 




.100 


16 


.250 




.220 


17 


.125 




.215 


83 


.625 




.460 


37 


.250 




1.000 


267 


2.812 




1.000 


52 


.437 












2.150 


104 


1.000 




.01 


27 


.125 




4.640 


288 


2.375 




.02 


22 


.125 




10.000 


781 


8.250 




.05 
.10 


24 
26 


.125 
.187 




.01 


10 


.062 




.20 


62 


.375 




.02 


14 


.062 




.50 


111 


.750 




.05 


16 


.125 




1.00 


182 


1.437 




.10 


30 


.125 




2.00 


419 


3.125 




.20 


28 


.187 




5.00 


1,371 


14.750 




.50 


54 


.437 












1.00 


89 


.750 












2.00 


163 


1.625 












5.00 


348 


4.687 










Manganese 


.010 
.022 
.046 
.100 
.215 
.464 
1.000 


376 
384 
406 
404 
361 
444 
434 


3.812 
3.875 
4.250 
3.937 
4.187 
4.375 
5.750 











'These element standards have a granitic matrix. 
2 120-sec I09cd irradiation. 



32 



TABLE B-4. - PXRFS ( 109 Cd) analysis of selected Bureau of Mines 

mineral display specimens 



Sample and 


Elements 




Element to 




composition (9) 


detected 


Counts 


backscatter 


Comments 




by PXRFS 




ratio 




Carnotite in sandstone; 


K 


77 


1.687 


30-sec irradiation. 


K 2 (U0 2 ) 2 (V0 4 ) 2 tiH 2 0. 


Ca 


66 


1.437 






Cu 


45 


1.375 






U 


213 


4.750 




Cinnabar and antimony ' . . . 


Hg 


123 


2.312 


60-sec irradiation. Sb not 




S 


39 


.250 


detectable with this 




Ca 


51 


.812 


instrument. 




Fe 


23 


.437 




Cupro-tungstate; CuO and 


Cu 


265 


9.375 


60-sec irradiation. W re- 


wo 3 . 1 


Fe 


170 


5.625 


sponse is masked by intense 




Co 


185 


6.312 


Cu response combined with 




Ni 


282 


9.187 


Ni and Co responses. 




Pb 


535 


17.312 






Ca 


50 


1.875 




Erythrite; 37.5% CoO, 


Co 


189 


( 2 ) 


30-sec irradiation. Overflow 


38.4% As 2 5 , 24.1% H 2 0. 


As 


184 


( 2 ) 


indicates a ratio is not 
possible because backscatter 
is nonexistent. 


Ferberite; 23.7% FeO and 


Fe 


94 


(2) 


Do. 


76.3% W0 3 . 


W 


175 


(2) 




Galena; 86.6% Pb and 


Pb 


580 


56.562 


60-sec irradiation. 


13.4% S. 


S 


42 


3.500 






Ca 


35 


4.500 






Fe 


62 


5.625 




Garnierite; (Ni,Mg)Si0 3 


K 


38 


3.375 


30-sec irradiation. 


•nH 2 0. 


Ni 


710 


57.000 






Ca 
Fe 


115 

24 


3.437 
.875 


60— sec irradiation. Double 




peak could be from Hg or Pb 




Au 


138 


4.500 


response as well as Au. 


Niccolite; 43.9% Ni and 


Ni 


156 


26.000 


30-sec irradiation. 


56.1% As. 


As 


84 


12.562 






Ca 


60 


8.000 




Rhodonite; 54.1% MnO and 


Mn 


671 


31.437 


45-sec irradiation. 


45.9% Si0 2 . 










Scheelite in granite; 


Ca 


93 


2.187 


60-sec irradiation. 


19.4% CaO and 80.6% W0 3 . 


W 


84 


1.500 






Fe 


54 


.812 






Rb 


4 


.250 




Scheelite and pyrite; 


Ca 


48 


1.062 


Do. 


19.4% CaO, 80.6% W0 3 , 


W 


78 


1.375 




46.6% Fe, 53.4% S. 


Fe 


120 


2.312 




Uranium in sedimentary 


U 


106 


.875 


Do. 


rock. ' 


Ca 


42 


.312 






Fe 


123 


1.062 




1 Exact comDosition percent 


not knowi 


l. 2n V 


srf low. 





33 

APPENDIX C— NUCLEAR REGULATORY COMMISSION (NRC) LICENSING INFORMATION 

All manmade radioactive materials are strictly controlled by the NRC, and it has 
issued comprehensive regulations for controlling and licensing radioactive isotope 
sources (called "byproducts" because of their origin in a nuclear reactor). 

Briefly, the NRC regulations require the following relative to the PXRFS: 

1. The licensing of any company or individual (including Government agencies) 
that uses isotopes of the strength required in portable X-ray fluorescence 
spectrometers. 

2. The isotopes be under the control of a trained and qualified person at all 
times. 

3. The material be kept reasonably secure against theft or loss by accident. 

4. Safety precautions be adequate to protect the user and others in the vicinity 
from radiation. 

5. An authorized individual user be present and directly supervise the use of 
the spectrometer at any temporary job site. 

6. User qualifications include, as a minimum, the completion of the instrument 
manufacturer's training course. 

7. Training by companies is permissible, but the NRC must approve the training 
course. 

8. If multiple users are listed on the license, a radiation protection officer 
must be named. 

"A Guide for Preparation of Byproduct Material Application for the Use of Sealed 
Sources in Portable and Semiportable Gauging Devices" can be obtained by writing: 
Materials Licensing Branch, Division of Fuel Cycle and Material Safety, Nuclear Regu- 
latory Commission, Washington, D.C. 20555. 



fcU.S. GOVERNMENT PRINTING OFFICE: 1982 - 505 - 002/65 



INT.-BU.OF MINES, PGH., PA. 26244 









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